Note: Descriptions are shown in the official language in which they were submitted.
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SOLAR PANEL SYSTEM
Field of the Invention
[0001] The invention relates to the art of solar panel systems, and in
particular to
actuation systems for controlling the azimuth and elevation angles of a solar
panel and to
system architectures for controlling large numbers of solar panels.
Background of the Invention
[0002] To obtain the maximum efficiency out of a solar panel it is necessary
to
change the position the panel to track the position of the sun as it moves
across the sky.
[0003] It is desirable for the solar panel actuator system to be robust, and
have a
long service life. In a solar farm, where thousands of panels may be deployed,
it may be
necessary to utilize thousands of solar panel actuators, so low cost is an
important
concern. Similar concerns arise for the consumer market.
[0004] Likewise, it may be necessary to control large numbers of solar panels
in
an efficient manner.
Summary of the Invention
[0005] According to one aspect of the invention a solar panel assembly is
provided which includes: a foundation tube; a rotary actuator mounted in the
foundation
tube, the actuator having a rotating plate extending out of an end of the
foundation tube; a
linear actuator having a stationary portion and an extensible portion; a
bracket mounted
to the rotating plate, the bracket having an arm mounted to one of the linear
actuator
stationary portion and the linear actuator extensible portion; and a frame for
holding a
photovoltaic panel, the frame being pivotally mounted to the bracket and the
frame
having an arm connected to the other of the linear actuator stationary portion
and the
linear actuator extensible portion.
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100061 The rotary actuator preferably includes: a motor; a gearbox driven by
the
motor; a drive screw connected to and driven by an output of the gearbox; a
spindle
screw connected to the rotating plate; a drive nut having a first threaded
hole for
receiving a thread of the drive screw and a second threaded hole for receiving
a thread of
the spindle screw, the guide nut having a guide fin; and a guide rail
interacting with the
nut guide fin to constrain the nut from rotating, whereby the rotation of the
drive by
screw by operation of the motor causes the nut to translate linearly which in
turn causes
the spindle screw to rotate.
[00071 The motor is preferably a low cost, brushed DC motor, of approximately
0.5 - 3 Nim output. The gearbox provides a gear reduction between an output of
the
motor and an output the gearbox, and wherein the turns ratio between the drive
screw and
the spindle screw provides a gear reduction between the drive screw and the
spindle
screw. Overall, a high reduction, e.g., 7500:1 gear reduction, is provided
between the
motor and rotating plate,
[0008] The guide rail is preferably provided in the form of a tubular housing.
The
motor and gear box are connected to the tubular housing. The drive screw,
spindle screw
and nut are each disposed with the tubular housing, and it has a channel for
receiving the
guide fin of the nut.
100091 The linear actuator preferably includes: a motor; a gearbox driven by
the
motor; a drive screw connected to and driven by an output of the gearbox; a
first tube
encompassing the drive screw, the first tube being connected to one of the
frame arm and
the bracket arm; a second tube partially mounted in and extensible from the
first tube, the
second tube being pivotally connected to the other of the frame arm and the
bracket arm
in a manner so as to prohibit substantive rotation of the second tube relative
to the first
tube; and a drive nut having a threaded hole for receiving a thread of the
drive screw, the
drive nut being disposed within the second tube and having a splined
connection to at
least one of the first and second tube in order to prohibit rotation of the
drive nut,
whereby the drive nut translates linearly causing the second tube to slide
linearly relative
to the first tube as the drive screw is rotated by said motor and gearbox.
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[0010] An end portion of the linear actuator drive screw distal of the gearbox
output is preferably connected to a concentric post that spaces the drive
screw away from
inner walls of the second tube. The non-connected end of the second tube
preferably
includes an end cap disposed within the first tube, the end cap and concentric
post
spacing the outer wall of second tube away from the inner wall of the first
tube. And the
end of the first tube distal from the gearbox preferably includes an annular
seal contacting
the outer wall of the second tube.
[0011] According to another aspect of the invention a rotary actuator is
provided
which includes: a motor; a gearbox driven by the motor; a drive screw
connected to and
driven by an output of the gearbox; a spindle screw, one end of which provides
an
output of the rotary actuator; a drive nut having a first threaded hole for
receiving a
thread of the drive screw and a second threaded hole for receiving a thread of
the spindle
screw, the guide nut having a guide fin; and a guide rail interacting with the
nut guide fin
to constrain the nut from rotating, whereby the rotation of the drive by screw
by operation
of the motor causes the nut to translate linearly which in turn causes the
spindle screw to
rotate.
[0012] According to another aspect of the invention a solar panel assembly is
provided which includes a stand and a photovoltaic panel pivotally mounted to
the stand
about a horizontal axis so as to be adjustable in elevation. A motorized drive
adjusts the
elevation of the panel. The power source is provided by at least first and
second batteries
and a motor drive circuit is connected to the batteries for powering the
motorized drive.
A stow sensor provides a signal indicating a command to move the panel to a
horizontal
position. A stow circuit receives the stow signal. In the nominal state, the
stow circuit
connects the at least first and second batteries in parallel and applies an
output of the
parallel-connected batteries to the motor drive circuit. This lowers the
voltage and
increases the current capacity of the batteries relative to a serial
connection and allows for
greater time before the energy in the batteries is depleted. However, in the
event the stow
signal is activated, the stow circuit connects the at least first and second
batteries in
series, disconnects the motor drive circuit from the motorized drive, and
applies an output
of the serial-connected batteries directly to the motor. This provides greater
voltage to
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the motorized drive and enables it to be driven faster. In addition,
disconnecting the
drive circuit allows the panel to be stowed even in the event of a software
error as the
stow circuit is preferably provided in the form of hardwired logic.
[0013] The stow signal may be activated in response to at least one of. a wind
speed sensor reading wind speeds above a predetermined amount; loss of local
controller
power; loss of charging current; a manual user command to stow; a software
malfunction;
and a master stow command.
Brief Description of the Drawings
[0014] The foregoing and other aspects of the invention will be more readily
appreciated having reference to the drawings, wherein:
[0015] Fig. 1 is a fragmentary perspective view of a drive unit for angular
and
azimuth control of a solar panel assembly;
[0016] Fig. 2 is an isolated assembly view of a rotary actuator employed in
the
solar panel assembly;
[0017] Fig. 3 is a fragmentary view of the rotary actuator, with a guide tube
and
other elements in Fig. 2 removed from view;
[0018] Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 2;
[0019] Fig. 5 is a front view of an upper portion of the rotary actuator shown
in
Fig.3;
[0020] Fig. 6 is an isolated assembly view of a linear actuator employed in
the
solar panel assembly;
[0021] Fig. 7 is a partial cross-sectional view taken along line VII-VII in
Fig. 6;
[0022] Fig. 8 is a fragmentary view of the linear actuator shown in Fig. 7,
taken
from a different perspective;
[0023] Fig. 9 is a system block diagram of a first control architecture for
controlling a plurality of solar panels according to a one embodiment;
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[0024] Fig. 10 is a system block diagram of a second control architecture for
controlling a plurality of solar panels according to a second embodiment;
[0025] Fig. 11 is a perspective view of the solar panel assembly including a
preferred photovoltaic panel;
[0026] Fig. 12 is a fragmentary view of a double screw rotary actuator, with a
guide tube and other elements removed from view; and
[0027] Fig. 13 is a detail view of a drive train used to spin the double screw
rotary
actuator shown in Fig. 12.
Detailed Description of the Invention
[0028] A. System Summary
[0029] Fig. 1 shows a solar panel assembly 10 comprising a photovoltaic panel
frame 12 (only the rear of which is shown) mounted onto a foundation tube 14.
The
assembly 10 includes a rotary actuator 16 installed within the foundation tube
14 for
varying the azimuth 18 of the panel frame 12 about a vertical axis 20 defined
by the
foundation tube 14. The assembly 10 also includes a telescoping linear
actuator 24 for
varying the elevation angle 26 of the panel frame 12 about a horizontal axis
28 defined by
a hinge shaft 30.
[0030] More particularly, the panel frame 12 includes a structural cross beam
32
able to support the weight of the panel frame 12 and any photovoltaic modules
mounted
thereon. The crossbeam 32 includes two spaced apart mounting flanges 34a, 34b
for
mounting the panel frame 12 onto a bracket 36. The bracket 36 features a
mounting plate
38 terminating in two uprising, spaced apart wings 40a, 40b. The hinge shaft
30 is
installed through openings in the spaced apart wings 40a, 40b and mounting
flanges 34a,
34b. Capstans or nuts 42 secure the hinge shaft 30.
[0031] The bracket mounting plate 38 is bolted onto a rotating plate 44 (seen
best
in Figs. 2 or 3) positioned atop the foundation tube 14, as discussed in
greater detail
below. The rotary actuator 16 rotates this plate 44, and hence the panel frame
12.
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[00321 The bracket 36 includes an arm 46 that supports a stationary portion 50
of
the linear actuator 24. An extensible portion 52 of the linear actuator 24 is
connected to
an arm 48 that is rigidly connected to the panel crossbeam 32. Thus, the
linear motion of
the extensible portion 52 is converted into pivotal motion of the panel frame
12 about the
hinge shaft 30.
[00331 B. Panel Frame
100341 Fig. 11 shows a preferred embodiment of the panel frame 12, which
includes a panel 400 having a flat front face 402 and a more complex rear face
404. The
front face 402A carries a plurality of solar cells or photovoltaic modules 420
such as
Mitsubishi TD190MF5 models which weigh about 40 pounds per module. As these
components are relatively heavy, e.g., collectively exceeding four hundred
pounds or so,
the rear face 404 of the panel 400 includes stiffening ribs 406 to reduce the
overall
thickness of the panel 400 for a given load. In the most preferred embodiments
the panel
400 is formed out of aluminum in a one-shot molding process known in the
automotive
arts as "superplastic forming" that is described, inter alia, in US Patent
5,974,847, which
is hereby incorporated by reference in its entirety. As such, the panel 400
can be formed
so that the stiffening ribs 406 or other structural support features are
integrally formed
with the flat front face 402. In the illustrated embodiment, the panel has a
breadth of
about 3.3 x 4.3 meters and the thickness of the panel 400 is about 3 mm,
giving the panel
an overall weight of about three hundred and sixty pounds. An aluminum cross-
beam
408 weighing about one hundred pounds is mounted to the panel 400 and
connected to
the rotary and linear actuators as described above. Still, with aluminum
plastic forming,
the panel frame 12 is expected to weigh less than a conventional steel
structure, enabling
the use of smaller rotary and linear actuators.
[00351 In the illustrated embodiment the stiffening ribs 406 are arranged as a
series of upper and lower rectangular-shaped stiffening members 410. The
stiffening
members increase the rigidity of the panel 400 to more effectively retain its
orientation to
the sun. In addition, the two rows of stiffening members 410 define a channel
therebetween for mounting the aluminum cross-beam 408. The rear face of the
panel 400
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can also be used to mount other electrical components thereto such as micro-
inverters
(not shown).
100361 C. Rotary Actuator
[00371 The rotary actuator 16 is shown in greater detail in the isolated views
of
Figs. 2 - 5. Referring additionally to these Figures, the rotary actuator 16
includes a
motor 60 driving a reduction gearbox 62 that in turn rotates a drive screw 64.
The drive
screw 64 is coupled by a nut 66 and a guide rail 68 to a spindle screw 70 that
is connected
to the rotating plate 44.
100381 More particularly, the guide rail 68 is provided in the illustrated
embodiment as a tubular guide 69 (seen best in the cross-sectional view of
Fig. 4) which
encompasses the drive screw 64, nut 66 and lead screw70. The tubular guide 69
includes
a fixedly mounted plug 72 at a bottom end thereof for sealing and supporting
the tubular
guide 69. The spindle screw 70 is rotationally mounted to the internal or top
side of the
plug 72 by a bearing 74. The motor 60 is fixedly mounted to the external or
bottom side
of the plug 72.
[00391 By way of example, a suitable motor is 1.2 Nm 12V brushed DC motor
manufactured by Harbin Electric of China.
100401 The gearbox 62 preferably provides a large gear reduction, e.g., a 26:1
reduction. The gearbox 62 is preferably identical to a gear box utilized in
the linear
actuator 24, as shown in Fig. 7 and discussed in greater detail below
100411 The output gear of the gearbox 62 is rigidly connected to the drive
screw
64, thus rotating the drive screw 64. A cover 75 shields the drives screw 64
in the portion
between the gearbox 62 and plug 72. This portion of the drive screw need not
be
threaded, and thus a tight tolerance may be provided between the shaft of the
drive screw
and a hole 77 formed in the plug 72 for passage of the drive screw
therethrough.
[00421 The other end of the drive screw 64 is rotatingly mounted via a small
axle
(not shown) to a base plate 76 that caps and plugs the open end of the
foundation tube 14.
(The rotating plate 44 lies above the open end of the foundation tube 14.) The
drive
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screw 64 thus rotates in situ. In the illustrated embodiment, the drive screw
64 is
preferably formed from steel and has a 3/ inch diameter, 8 turns per inch,
Acme thread.
10043] The nut 66 is preferably formed from Acetal or other hard plastic with
lubricating properties. As seen best in Fig. 4, the nut 66 has two threaded
nut holes 78,
80, one 78 to matingly receive the threads of the drive screw 64, and the
other 80 to
matingly receive the thread of the spindle screw 70. The nut 66 also features
two
opposing guide fins 82a, 82b that each fit into two opposing channels 84a, 84b
formed in
the guide tube 69.
100441 As seen best in Fig. 5, the spindle screw is journaled to the base
plate 76
via a bushing 86 that fits over the spindle screw 70. The rotating plate 44 is
bolted to the
to an end shoulder of the spindle screw 70, or alternatively to bushing 86,
and a series of
ball, roller and/or other type of bearing 87 is positioned between the
rotating plate 44 and
the base plate 76 to enable the former to smoothly slide over the latter.
10045] The spindle screw 70 preferably features a dual start, low turn ratio,
lead
thread 88. In the illustrated embodiment, the lead screw has a 0.03 turns per
inch thread
on a 2.4 diameter, hollow aluminum shaft. The thread 88 preferably has
approximately
240 of turn over the length of the spindle screw 70, which is sufficient to
meet the east -
west tracking requirements of the solar panel. Overall, with the 26:1
reduction provided
by the gearbox 62 and an approximately 285 turns ratio between the drive screw
64 and
the spindle screw 70, an approximately 7500:1 reduction is provided between
the motor
60 and the spindle screw 70. Those skilled in the art will appreciate that a
wide variety of
other component dimensions and drive ratios may be employed in a commercial
rotary
actuator.
100461 In operation the motor 60 and gearbox 62 rotate the drive screw 64,
which
is constrained to spin in situ. The nut 66 receives the torque provided by the
drive screw
64, however, the nut 66 is prevented from rotating due to the entrapment of
its guide fins
82a, 82b within the channels 84a, 84b of the tubular guide 69. Accordingly,
the nut 66
translates linearly upon receipt of the torque imparted by the drive screw 64.
As the nut
66 translates, it will in turn impart torque to the spindle screw 70, causing
the spindle
screw to likewise spin in situ, and in the process turn the rotating plate 44.
Clearly,
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operating the motor in one rotational sense will cause the rotating plate to
turn in a first
rotational sense and operating the motor in the opposite rotational sense will
cause the
rotating plate to turn in a second, opposite rotational sense.
[0047] Advantageously the rotary actuator 16 may be preassembled as an
independent unit and slid into the foundation tube 14 as a unit. An
electronics box 60
may also be attached to the guide tube 68 and thus mounted in the foundation
tube 14.
The base cap 76 seats on a reinforcing flange 92 situated at the top of the
foundation tube
14, and a water and dust shield 94 (Fig. 1) covers the base cap 76 and
rotating plate 44.
[0048] Fig. 12 shows the innards of an alternative rotary actuator 500, which
has
two drive screws contained with a guide tube (not shown). The rotary actuator
500
includes motor 60 driving a reduction planetary drivetrain 562 that rotates
two drive
screws 564a. 564b. The drive screws 564a, 564b are coupled by a nut 566 and
the guide
tube (not shown) to spindle screw 70 that is connected to rotating plate 44.
The nut 566
has three threaded nut holes 578a, 578b and 580; two 578a and 578b to matingly
receive
the threads of the drive screws 564a, 564b, respectively, and the other 580 to
matingly
receive the thread of the spindle screw 70. The nut 566 also features two
opposing guide
fins 582a, 582b that each fit into two opposing channels formed in the guide
tube.
[0049] Fig. 13 shows the reduction planetary drivetrain 562 in greater detail.
The
motor 60 drives a pinion gear 562a. The pion gear 562a drives two first stage
spur gears
562b. The two first stage spur gears 562b each drive a second stage spur gear
562c
which, in turn, each drive a third stage gear 562d that is rigidly connected
to one of the
drive screws 564a, 564b.
[0050] The rotary actuator 500 works substantially similar to that of the
single
screw rotary actuator 16. The addition of another drive screw helps to even
out the
torques experienced by the assembly and reduce bending moments and other
stresses on
the relatively long drive components.
[0051] D. Linear Actuator
[0052] The linear actuator 24 is shown in isolation in Figs. 6 to 8. The
stationary
portion 50 of the linear actuator includes a motor 100, gearbox 102 and a base
or outer
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tube 104. The extensible portion 52 includes an inner tube 106 that fits
within the outer
tube 104 and extends therefrom.
[0053] The motor 100 may be the aforementioned 1.2 Nm. 12 volt brushed DC
motor. As seen best in Fig. 7, the motor 100 has an output shaft 108 coupled
to a spur
gear 110 mounted in the gearbox 102. The spur gear 110 drives a first
reduction gear 112
that is mounted on a shaft 114 journaled in the gearbox 102. The shaft 114
also contains
a second spur gear 116 that drives an output gear 118. Sleeve bearings 120
journal the
shafts 108, 114 within the gearbox 102.
[0054] The output gear 118 is fixed at its rotational axis to a drive screw
124.
The drive screw 124 has a non-threaded butt end portion which is journaled in
the
gearbox via two large tapered roller bearings 126. The drive screw in the
illustrated
embodiment is a 3/ inch diameter, 8 turns per inch, stainless steel screw.
[0055] The stationary outer tube 104 is preferably adhesively bonded to the
walls
of an inlet 128 in the gearbox. A fixture 130 (Fig. 6) is attached to the
exterior of the
outer tube 104 and mounted to the arm 46 of the bracket 36. The outer tube 104
includes
a concentric wiper seal 132 (Fig. 8) at the end of the tube 104 distal of the
gearbox 102,
the seal 132 contacting the extensible tube 106 to prevent dirt from entering
the system.
[0056] The extensible inner tube 106 fits within the stationary outer tube 104
and
partially encompasses the drive screw 124. A drive nut 104 is fitted over the
drive screw
124 and has threads that matingly receive the threads of the drive screw 124.
The drive
nut is positioned within extensible inner tube 106 and has two opposing
splines 137 that
engage two slots (not shown) in the extensible inner tube 106.
[0057] The extensible inner tube 106 includes an end cap 136 to seal the inner
tube 106 against the interior wall of the outer tube 106. The end cap 136 also
enables a
small gap to be maintained between the exterior wall of the inner tube 106 and
the
interior wall of the outer tube 104, and the cap is preferably formed from a
slick material
in order to minimize friction as the cap slides along the interior wall of the
outer tube
104. Likewise the drive screw 124 includes a centralizing post 138 that
assists in
maintaining good clearance between the drive screw 124 and the walls of the
extensible
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inner tube 106 and the post 138 is preferably formed from a slick material in
order to
minimize friction as the extensible inner tube 106 slides.
[00581 The end of the extensible inner tube 106 distal from the motor includes
an
attachment member 140 that features a pinned connection 142 for coupling the
extensible
inner tube 106 to the arm 46 connected to the panel crossbeam 32.
[00591 In operation, the motor 100 and gearbox 102 rotate the drive screw 124,
which spins in situ. The drive nut 134 receives the torque from the drive
screw 124 but is
constrained from rotating due to its splined interconnection with the inner
tube 106,
which is itself precluded from rotating as a result of the pinned connection
142 with the
arm 46. Consequently the drive nut 134 translates linearly, moving the inner
extensible
tube 106 relative to the stationary outer tube 106. Those skilled in the art
will appreciate
that the drive nut could additionally or alternatively have a splined
interconnection with
the outer tube and be used to push the inner tube outward or collapse it
inwards, for
example, by placing the drive nut between two interference features within the
inner tube.
[00601 It will also be appreciated that while the illustrated embodiment has
the
arm bracket 46 connected to the stationary portion 50 of the linear actuator
and the
crossbeam arm 48 connected to the extensible portion 52 of the linear actuator
the
opposite arrangement may be effected in alternative embodiments. In other
words, in an
alternative embodiment, arm bracket 46 is connected to the extensible portion
52 of the
linear actuator and the crossbeam arm 48 is connected to the stationary
portion 50 of the
linear actuator 24.
[00611 E. Electronics
[0062) Fig. 9 shows one embodiment of a control architecture for controlling a
plurality of solar panels, for example, in the deployment of a solar farm. In
this
architecture, a subgroup of panels 200 are controlled by a local master 202
that connects
via a network controller 204, such as an Ethernet controller or Controller
Area Network
(CAN) controller, to a master controller 207 via a wire or wireless
communication link
206. In this embodiment, the local master 202 includes a 12 volt 50 or 60 amp
hour
battery 208 and a charger 210 which uses energy harvested from the solar
panels to
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charge the battery 208. The battery charge, in turn, is fed out as a 12 volt
DC signal 218
to supply the electronics driving each individual panel 200. The local master
202 also
includes a DC to AC converter or inverter 212 which receives the electricity
generated by
the solar panels 200 in lines 216 and converts the DC power to an AC power
voltage 214
for distribution to the power grid via a phase matching transformer.
[0063] In this embodiment each solar panel 200 also includes a local
controller
220. The local controller 220 includes a microcontroller 222 which
communicates with
the local controller preferably via a wired communications link 226 such as
provided by
CAN controller 224. The actuation system for repositioning the solar panel may
be
controlled by commands received over the communication links 204, 206, 224,
226 and
executed by the microcontroller 222 which, in turn, controls the motors of the
rotary and
linear actuators via motor control lines 228, 230.
[0064] Figure 10 shows another embodiment of a control architecture omitting
the local master. In this architecture, each solar panel 200 is associated
with a local
controller 300. The local controller 300 includes a microcontroller 302 which
communicates with a master controller (not shown) via a network controller
304, such as
may be provided by an Ethernet controller or CAN controller, and communication
link
306. The local controller 300 incorporates a small (e.g., 3 amp) power supply
and trickle
charger 308 which is directly fed with line 120 volt AC power 309. In this
embodiment,
every solar panel 200 includes a rechargeable battery 310 (see also Fig. 2)
which is
charged by the power supply and trickle charger 308. A DC to AC converter 212
is
provided for receiving the electricity generated by the solar panels 200 in
lines 216 and
converts the DC power to a high voltage AC signal 214 for distribution to the
power grid.
The position of the solar panel is controlled by providing operational
commands to the
microcontroller 302 which, in turn, controls the motors of the rotary and
linear actuators
via control lines 228, 230.
[0065] Fig. 14 shows a circuit diagram of a hard wired stow control circuit
600.
The photovoltaic panel 12 has a relatively large cross-sectional area that can
be subject to
considerable wind loads. At certain times, it is desirable to place the solar
panel
assembly 10 in a stow condition wherein the panel 12 is placed horizontal to
the ground.
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A stow condition can be: wind speeds higher than 35km/h (reading provided by
wind
speed sensor, not shown); loss of local controller power; loss of charging
current; manual
user command to stow; software malfunction; and a master stow (gang system)
command.
[00661 In the preferred embodiment motor two rechargeable batteries 31 Oa, 31
Ob
are used to power the actuators and the drive electronics. The two batteries
310a, 310b
are each preferably 12 volt batteries that are normally connected in parallel.
This doubles
the current capacity of the system, and increases the amount of time the
system can
operate without recharging the batteries. However, during a stow condition,
the circuit
600 automatically reconfigures the batteries 31 Oa in series to operate at
least the linear
actuator motor at 24 volts. This increases the speed of the motor(s) thereby
reducing the
time it takes to bring the photovoltaic panel 12 to the horizontal position.
100671 The stow control circuit 600 is shown in Fig. 14 in its nominal
operating
state. In this state relay RL2 connects the negative terminal of battery 31Ob
to ground
and relay RL4 connects the positive terminal of battery 310a to the positive
terminal of
battery 31 Ob. The batteries 310a, 310b are thus connected in parallel and
feed
conventional motor drive circuitry 602. Note that in this state relays RLI and
RL3 are
configured to apply 12 volt power modulated by the motor drive circuitry 602
to the
linear actuator motor 100.
[0068] However, when a stow condition is detected on any of signal lines 604,
relays RL1 and RL3 are energized to switch out the motor drive circuitry 602
and directly
apply power from the batteries 31 Oa, 31 Ob to the linear actuator motor 100.
In this state,
relays RL2 and RL4 also energize. Relay RL2 disconnects the negative terminal
of
battery 31Ob from ground, and relay RL4 connects the positive terminal of
battery 31 Oa
to the negative terminal of battery 31 Ob. Thus, the batteries are connected
in series to
apply 24 volts to the motor 100. As soon as this happens the linear actuator
motor 100
starts driving the solar photovoltaic panel to the horizontal position.
100691 Note that all of these actions can be done with or without software
algorithm supervision. Thus, upon a software malfunction the hard wired logic
provided
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by the circuit 600 will take control of the system and safely stow the solar
photovoltaic
panel.
100701 While the above describes a particular embodiment(s) of the invention,
it
will be appreciated that modifications and variations may be made to the
detailed
embodiment(s) described herein without departing from the spirit of the
invention.
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